Dynamical seasonal prediction using the global environmental multiscale model with a variable resolution modeling approach     

Marko Markovic  Hai Lin  Katja Winger 《Climate Dynamics》2012,39(7-8):1885-1904

In this work we evaluate seasonal forecasts performed with the global environmental multiscale model (GEM) using a variable resolution approach and with a high-resolution region over different geographical locations. Therefore, using two grid positions, one over North America and the other over the tropical Pacific-eastern Indian Ocean, we compare the seasonal predictions performed with the variable resolution approach with seasonal forecast performed with the uniform grid GEM model. For each model configuration, a ten-member ensemble forecast of 4?months is performed starting from the first of December of selected ENSO winters between 1982 and 2000. The sea surface temperature anomaly of the month preceding the forecast (November) is persisted throughout the forecast period. There is not enough evidence to indicate that a Stretch-Grid configuration has a clear advantage in seasonal prediction compared to a Uniform-Grid configuration. Forecasts with highly resolved grids placed over North America have more accurate seasonal mean anomalies and more skill in representing near surface temperature over the North American continent. For 500-hPa geopotential height, however, no configuration stands out to be consistently superior in forecasting the ENSO related seasonal mean anomalies and skill score.  相似文献   

Analytical modelling of wintertime coastal jets in the Adriatic Sea     

Martin Lazar  Marko Pavić  Zoran Pasarić  Mirko Orlić 《Continental Shelf Research》2007

Two diagnostic models, reproducing circulation generated in a marginal sea by variable density, have been developed. The models’ domain is a 2D transverse section for which analytical solutions have been obtained. They describe the winter situation in the northern Adriatic, with a strong vertical mixing present and the density maximum dominating the centre of the basin. Both models employ Boussinesq-type parametrisation of friction and linear slip at the bottom. The first model allows for frictional departure from hydrostatic equilibrium and includes vertical friction only. The second one is hydrostatic but allows for lateral friction as well. The results obtained by the two models are similar and to some extent dependent on the vertical and bottom friction. They reproduce several well known characteristics of the Adriatic circulation (cyclonic surface flow, downwelling in the central and larger part of the basin compensated by upwelling in the coastal zone) but also predict some phenomena that are still not well understood. A conspicuous feature of the model results are coastal jets, which were observed in the Adriatic on several occasions. The present models show that the distance of jets from the coasts depends on lateral friction: it is found to vary from 1 up to 10 km on the Italian side and between 2 and 15 km on the Croatian side. Both models reproduce the west–east asymmetry, with the wider current on the east side of the basin. The asymmetry is a subject on which conflicting empirical results exist in the Adriatic. In the two models cyclonic flow occupies the whole water column, which disagrees with some recent theoretical findings of the near-bottom anticyclonic flow and thus leaves the issue open.  相似文献   

A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa     

Linnemann  Ulf  Pidal  Agustín Pieren  Hofmann  Mandy  Drost  Kerstin  Quesada  Cecilio  Gerdes  Axel  Marko  Linda  Gärtner  Andreas  Zieger  Johannes  Ulrich  Jens  Krause  Rita  Vickers-Rich  Patricia  Horak  Jana 《International Journal of Earth Sciences》2018,107(3):885-911

International Journal of Earth Sciences - In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such...  相似文献   

Climate parameters of Estonia and the Baltic Sea region derived from the high-resolution reanalysis database BaltAn65+     

Aarne Männik  Marko Zirk  Rein Rõõm  Andres Luhamaa 《Theoretical and Applied Climatology》2015,122(1-2):19-34

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Using Temperature Fluctuation Measurements to Estimate Meteorological Inputs for Modelling Dispersion During Convective Conditions in Urban Areas     

Wenjun Qian  Marko Princevac  Akula Venkatram 《Boundary-Layer Meteorology》2010,135(2):269-289

We examine the performance of several methods to estimate meteorological inputs for modelling dispersion in urban areas during convective conditions. Sensible heat flux, surface friction velocity and turbulent velocities are estimated from measurements of mean wind speed and the standard deviation of temperature fluctuations at a single level on a tower at two suburban sites and at one urban site in Riverside, California. These estimates are compared with observations made at these sites during a field study conducted in 2007. The sensible heat flux is overestimated in the urban area, while it is underestimated at a suburban site when temperature fluctuations are used in the free convection formulation to estimate heat flux. The bias in heat flux estimates can be reduced through a correction that depends on stability. It turns out that the bias in heat flux estimates has a minor effect on the prediction of surface friction velocity and turbulent velocities. Estimates of sensible heat flux, surface friction velocity and turbulent velocities are sensitive to estimates of aerodynamic roughness length, and we suggest estimating the aerodynamic roughness length through detailed micrometeorological measurements made during a limited field study. An examination of the impact of the uncertainty in estimating surface micrometeorology on concentrations indicates that, at small distances from a surface release, ground-level concentrations computed using estimates of heat flux and surface friction compare well with the those based on observed values: the bias is small and the 95% confidence interval of the ratio of the two concentrations is 1.7. However, at distances much larger than the Obukhov length, this confidence interval is close to 2.3 because errors in both friction velocity and heat flux affect plume spread. Finally, we show that using measurements of temperature fluctuations in estimating heat flux is an improvement on that based on the surface energy balance, even when net radiation measurements are available.  相似文献   

In situ micro‐Raman and X‐ray diffraction study of diamonds and petrology of the new ureilite UAE 001 from the United Arab Emirates     

Dominik C. HEZEL  Leonid DUBROVINSKY  Lutz NASDALA  Jean CAUZID  Alexandre SIMIONOVICI  Marko GELLISSEN  Thorbjörn SCHÖNBECK 《Meteoritics & planetary science》2008,43(7):1127-1136

Abstract— A new olivine‐pigeonite ureilite containing abundant diamonds and graphite was found in the United Arab Emirates. This is the first report of a meteorite in this country. The sample is heavily altered, of medium shock level, and has a total weight of 155 g. Bulk rock, olivine (Fo_79.8–81.8) and pyroxene (En_73.9–75.2, Fs_15.5–16.9, Wo_8.8–9.5) compositions are typical of ureilites. Olivine rims are reduced with Fo increasing up to Fo_96.1–96.8. Metal in these rims is completely altered to Fehydroxide during terrestrial weathering. We studied diamond and graphite using micro‐Raman and in situ synchrotron X‐ray diffraction. The main diamond Raman band (LO = TO mode at ?1332 cm^?1) is broadened when compared to well‐ordered diamond single crystals. Full widths at half maximum (FWHM) values scatter around 7 cm^?1. These values resemble FWHM values obtained from chemical vapor deposition (CVD) diamond. In situ XRD measurements show that diamonds have large grain sizes, up to >5 μm. Some of the graphite measured is compressed graphite. We explore the possibilities of CVD versus impact shock origin of diamonds and conclude that a shock origin is much more plausible. The broadening of the Raman bands might be explained by prolonged shock pressure resulting in a transitional Raman signal between experimentally shock‐produced and natural diamonds.  相似文献   

Provenance of the HP–HT subducted margin in the Variscan belt (Cabo Ortegal Complex,NW Iberian Massif)          下载免费PDF全文

R. Albert  R. Arenas  A. Gerdes  S. Sánchez Martínez  L. Marko 《Journal of Metamorphic Geology》2015,33(9):959-979

The Variscan Upper Allochthon is a continental‐affinity terrane that recorded a Cambrian–Ediacaran magmatic arc generation, a subsequent transition to a passive margin, and a collision‐related high‐P metamorphism during the Devonian–Carboniferous amalgamation of Pangea. The objective of this article is to decipher which continental margin subducted in the Devonian high‐P–high‐T (HP–HT) event. To do so, a provenance study is presented using combined U–Pb (n = 613) and Lu–Hf (n = 463) isotopic LA–ICP–MS zircon analyses and Sm–Nd whole–rock (n = 5) determinations. These analyses have been performed on five samples of the Banded Gneisses (Cabo Ortegal Complex, NW Iberia), which forms a part of the HP–HT bottom member of the Upper Allochthon. Palaeozoic–Neoproterozoic zircon ages (34.7%) have a maximum abundance at 522–512 Ma, peaks at 575, 561, 545 Ma and minor abundance peaks between 780 and 590 Ma, and show from their Lu–Hf compositions a volcanic arc mixing pattern. This arc was probably related to the Cadomian arc system. The Mesoproterozoic population is scarce and scattered (2.8%), and due to its Lu–Hf pattern, it is proposed that this population is also West Africa Craton derived. The Paleoproterozoic population (39.6%) is concentrated at 2.07 Ga and it is linked to the Eburnean Orogeny, where depleted mantle derived magmas intruded an Archean craton margin. This craton is represented by the Archean population (22.8%), which is grouped at 3.0, 2.68‐2.61 and 2.52‐2.48 Ga, and shows long‐term reworking processes and at least two juvenile magma intrusions. These data show that the Variscan Upper Allochthon has a West African provenance and therefore, it strongly suggests that the NW Iberian allochthonous complexes and their correlative European terranes are also West Africa derived. These results allow us to finally clarify that the first high‐P event, recorded during the eo‐Variscan amalgamation of Pangea, was attained by the subduction of the margin of Gondwana under Laurussia.  相似文献   

Landslides at a uranium mill tailing deposit site Boršt (Slovenia) detected by radar interferometry     

Magda Čarman  Mateja Jemec Auflič  Marko Komac 《Landslides》2014,11(3):527-536

This paper presents a comparison of persistent scatterer interferometry (PSI) monitoring results with in situ displacement measurements at the November 1990 landslide at the Bor?t uranium mill tailing deposit site after heavy rain. Although the landslide did not directly endanger people, site remediation works were undertaken due to the subsequent environmental problems. Additionally, in situ monitoring with benchmarks was established in order to detect the ground motion of the landslide body. PSI campaigning in the ?kofjelo?ko-Cerkljansko area, where the uranium mill tailing is situated, performed for the purpose of measuring displacements of natural targets near the active landslide area, also detected displacements, most probably indicating a creeping process. When comparing the pre- and post-remediation velocities at the benchmarks located on the landslide with persistent scatterers (PSs) located near the landslide, the rates could be regarded as background. The results show that the remediation works in the form of a drainage tunnel were very effective as post-remediation velocities at the landslide closer to the PSs resembled the velocities of the PSs, while the velocities of the landslide mass above the drainage tunnel slowed down, even to below the background velocities. The high correlation values between the movements of the benchmarks and the PSs also confirm that the remediation works were effective as the fluctuations in the displacement values of the landslide were very similar to those of the PSs. Nevertheless, although there are several limitations in comparing the two different datasets, the PSI technique can be complementary to conventional in situ methods.  相似文献   

Small icebergs and iceberg fragments off Newfoundland: Relationships to deterioration mechanisms and the regional iceberg population     

J.R. Marko 《大气与海洋》2013,51(3):549-579

Abstract

Several sets of previously compiled data on iceberg size distributions in areas between North America and Greenland are compared and analyzed. The obtained results indicate that populations of icebergs with lengths L ≥ 20 m are well‐described by log‐normal and gamma distributions together with statistical parameters which are compatible with existing understanding of regional iceberg deterioration and change processes. A lesser amount of data on size distributions in Newfoundland icebergs with L < 20 m show occurrence probabilities which increase exponentially with decreasing iceberg length. Evidence is presented to show that these data are most consistent with the dominance of fracture processes in determining iceberg occurrence versus length relationships. Physical arguments are presented to suggest that the key fracture events are initiated in the larger icebergs by coincidences of wave‐generated bending stress maxima and randomly distributed structural flaws. Similar considerations and use of a simple sequential fracture model imply that size distributions in icebergs (and iceberg fragments) with L < 20 m are more consistent with the presence of an alternative, spontaneous failure mechanism also acting at randomly distributed structural defects. The implications of these results for forecasting and monitoring populations of small icebergs are discussed.  相似文献   

Comments on “on the deterioration of icebergs in the marginal ice zone” (Venkatesh et al., 1994)     

J.R. Marko  D.B. Fissel 《大气与海洋》2013,51(1):187-189

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